Japanese Laid-open Patent Publication Nos. 2007-94994 and 2007-193451 disclose virtual switches for virtualizing an actual (physical) disk at a network layer (switch layer) and providing users with a virtual disk independent of a host apparatus and a type of the actual disk.
FIG. 16 illustrates a known storage system 80. As illustrated in FIG. 16, a virtual switch 81 in the storage system 80 is arranged between a plurality of host apparatuses 82-1 through 82-3 (three host apparatuses in FIG. 16) and a plurality of actual disks 83-1 and 83-2 (two physical disks in FIG. 16).
The virtual switch 81 connects to the plurality of host apparatuses 82-1 through 82-3 and the plurality of physical disks 83-1 and 83-2 via a communication line of fibre channel (FC). The virtual switch 81 also connects to a management terminal 84 via a communication line (data transfer system) such as local area network (LAN).
The virtual switch 81 performs major functions by assigning a logical volume of any capacity sliced from each of the physical disks 83-1 and 83-2 to each of the host apparatuses 82-1 through 82-3. One major function (referred to as virtual disk function) is to provide users with at least one of the virtual disks (four virtual disks 85-0 through 85-3 in FIG. 16), independent of the host apparatuses 82-1 through 82-3 and the type of physical disks 83-1 and 83-2. Another major function (referred to as copy function) is to execute a copy process by splitting the copy process into a plurality of unit copy operations, each unit copy operation including a predetermined size, and performing the unit copy operations using a resource within the virtual switch 81 only, without using resources in the host apparatuses 82-1 through 82-3 (such as central processing units (CPUs) and memories).
The copy process includes backing up or moving data of a physical disk (for example, the physical disk 83-1 in FIG. 16) as a copy source onto a physical disk as a copy destination (for example, the physical disk 83-2 in FIG. 16) in accordance with content input to the management terminal 84.
The copy process based on the copy function is executed by a redundant arrays of inexpensive disks (RAID) device forming the physical disks 83-1 and 83-2 when the data of the physical disks 83-1 and 83-2 is periodically backed up or when data is moved from one of the physical disks 83-1 and 83-2 to a new disk when the one of the physical disks 83-1 and 83-2 is replaced with the new disk.